Plane Spotting

When he sees vapor trails in the skies above the Lower Rhine area, sys admin Charly Kühnast doesn't just dream of faraway places. With a Linux system and a DVB-T stick, he grabs the signals from jets flying overhead and tracks their courses on a map.

Most commercial aircraft have an Automatic Dependent Surveillance--Broadcast system on board; this is known as ADS-B for short. It constantly transmits the heading, altitude, speed, GPS position, and flight number on a frequency of 1,090MHz.

If you want to track the position of the jets yourself, you do not necessarily require an airport tower full of technology. All I needed was a Linux computer and a receiver for digital terrestrial television (a.k.a. a DVB-T stick for less than EUR 20, or about US$ 25); the stick uses the Realtek RTL 2832U chipset in conjunction with an E4000 or R820T tuner. In addition to this, I had two software components waiting on the runway: RTL-SDR and Dump1090.

RTL-SDR [1] supports communication with the DVB-T receiver, and Dump1090 [2] decodes the data obtained in this way using a mini-web server to display a map of the machines in the vicinity. Even if you do find the two components on your Linux system, the version is likely to be outdated. It thus makes sense to build the current versions yourself. The tools required for this are shown in the command in the first line of Listing 1. The following lines then fetch RTL-SDR and compile the RTL-2832U driver.

Listing 1

Installing Components

Drivers on a Collision Course

The next step is to create the /etc/modprobe.d/rtlsdr.conf file and write the following line:

blacklist dvb_usb_rtl28xxu

This prevents Linux loading the DVB-T driver that I would need to watch TV programs rather than planes. Now a reboot is necessary. The installation of Dump1090 is similarly simple. The following commands

copy and compile the software. When I point my browser at the URL http://127.0.0.1:8080, it now shows me a map in which I can zoom in on the location of my DVB-T receiver. To whet your appetite, I have posted a live demo of the airspace on the web [3]. Figure 1 shows a Ryanair jet landing at the provincial airport in Weeze, Germany. Life's exciting when you're part of the cabin crew.

Figure 1: Not exactly an international air traffic hub, but at least it proves that there are some aircraft movements over Charly's head.

Charly Kühnast is a Unix operating system administrator at the Data Center in Moers, Germany. His tasks include firewall and DMZ security and availability. He divides his leisure time into hot, wet, and eastern sectors, where he enjoys cooking, freshwater aquariums, and learning Japanese, respectively.